Abdominal aortic aneurysms (AAA) 12 as shown in FIG. 1 require surgical treatment to prevent rupture of the AAA sac and resulting mortality. The conventional surgical procedure for treatment of an AAA uses a transabdominal or retroperitoneal surgical approach that involves surgically exposing the aneurysm and replacing a diseased aortic segment including the AAA sac with an in-line endograft. The AAA is excluded from pressurized blood flow by clamping the aorta 2 with the use of an aortic prosthesis of appropriate size that is sutured just proximally below the renal arteries and distal to the two iliac arteries 4. The sac is cleaned and back bleeders are treated. A vascular graft is placed in the aorta and sutured proximal and distal the aneurysm. Once the graft is in place, the sac is folded over the graft and sutured and the aorta is unclamped and blood flow is allowed to resume.
The transabdominal or retropariteneal surgical treatment for AAA is highly invasive, requiring a large incision in the abdomen and occlusion of blood flow in the aorta. This treatment has a demonstrated operative mortality rate of about 3 percent for optimally selected patients, and is unfavorable for octogenarians and high-risk patients with multiple disorders. Also, this treatment requires an average hospital stay of about 12 days and a progressive recovery time of months, adding substantially to the cost of the procedure.
Another treatment for AAA involves endovascular placement of a stent-graft 20 to bypass the aneurysm, as shown in FIG. 2. One such stent-graft is disclosed in U.S. Pat. No. 4,655,881, which is incorporated herein by reference. This stent graft comprises co-knitted stent (wire loops) 22 and graft (fabric loops) 24. Such a stent-graft 20 may be introduced intravascularly, typically under fluoroscopic guidance, through an opening formed in an iliac artery in the groin into the abdominal aorta 2 using a delivery catheter. The stent-graft may be radially self-expanding in an unrestrained condition, in which case, it would be constrained during delivery to the location of the aneurysm. The stent-graft may be fixed to the aortic wall proximal and distal the aneurysm 12 by expansion of the stent-graft or by hooks that fixate and seal the proximal and distal attachment sites to the iliac artery and aortic walls, respectively.
Alternatively, the stent-graft may be delivered to the location of the aneurysm and expanded by a balloon. The stent-graft is crimped onto the balloon which is introduced intravascularly through an opening in an iliac artery using a catheter. When the balloon and stent-graft are positioned at the location of the aneurysm, the balloon is expanded by pumping fluid into the balloon. The balloon is then deflated and withdrawn through the iliac artery. It should be noted that both the self-expanding stent-graft and the balloon expanding stent-graft described above are introduced with the blood flow in the aorta interrupted.
The endovascular approach is less traumatic and has demonstrated a lower morbidity rate, quicker recovery, and lower cost than the transabdominal or retropariteneal surgical approach. The endovascular approach has shown promise in treating infrarenal AAA, isolated thoracic aortic aneurysm, and even isolated peripheral traumatic aneurysms. The endovascular approach, however, is compromised by several complications. One such complication is the occurrence of endoleaks. Size and topographical differentials between the stent-graft and the aorta can result in a persistent blood flow outside the lumen of the endovascular stent-graft into the aneurysmal sac following placement of the endovascular stent-graft. Endoleaks can also be caused by incomplete apposition of the attachment sites against the aortic wall. Since pressurized blood flow continues to reach the anuerysmal sac, sac rupture can result. Accordingly these leaks are known as type I endoleaks. Another type of endoleak can occur as a result of the patient's inferior mesenteric artery and lumbar vessels continuing to feed the aneurysmal sac laterally. This type of endoleak has the potential to result in sac rupture. A second complication that can occur with the endovascular approach using a stent-graft is a condition called “stent abrading.” Other complications that can occur with the endovascular approach include: balloon malfunction, prosthesis (i.e., stent-graft) migration, stent-graft thrombosis and inadvertent obturation of renal arteries.
To overcome the shortcomings of existing treatments for AAA, a need exists for a minimally invasive and minimally traumatic treatment of AAA that reduces the risks of endoleaks, graft migration, graft thrombosis, obturation of renal arteries, and stent abrading. Comparable problems and needs can be identified in the treatment and devices used for surgical and endoluminal repair of defects in other body lumens.